Technique for notification of mobile terminals by geographical co-ordinates

ABSTRACT

The present invention provides a wireless telecommunications network comprising at least one base station transmitter and a plurality of user equipments able to receive radio messages from the at least one base station transmitter. The network is adapted to transmit a notification message to at least a sub group of the user equipments, a first part of the message comprising a representation from which a user equipment can determine whether its present location is within a certain geographical area. Once the user equipment has determined that it is within this area a second part of the message is read. This second part preferably includes a reason for the notification, e.g. a description of an emergency. To read this message the user equipment may be required to access the network so that the use of the service can be billed.

[0001] The present invention relates to wireless communication systemssuch as Public Mobile Radio (PMR) and Cellular Telephone systems as wellas wireless notification or paging systems and satellite communicationssystems and to methods of operation thereof.

TECHNICAL BACKGROUND

[0002] In wireless systems, paging is used when the network needs tocontact a user terminal (UE) which is not currently communicating withthe network or cannot communicate with the network—e.g. in a systemusing pagers having no communication possibility. For example, inwireless cellular telephone systems a UE is paged when it has gone intoa mode where it uses discontinuous reception. There are generally twoadvantages associated with the use of paging for wireless cellulartelephone systems:

[0003] It allows a mobile UE to move within a list of cells, typicallywithin a Location Area, or from one radio coverage area to anotherwithout informing the network. This reduces the signalling trafficbetween UE's and the network which only deals with the position of theUE.

[0004] It allows a mobile UE in a particular cell or radio coverage areato use a reduced duty cycle when idle by only monitoring a pagingchannel, therefore reducing battery consumption.

[0005] The objective of paging is typically to contact the UE and totransfer a message. The message may include an implicit or explicitrequest for the UE to contact the network by sending a random accessrequest on an access channel. In this way, communications can be set upbetween a mobile UE and the network.

[0006] Paging can be used towards individual UE's or to groups of UE's,typically as a notification channel in case of activity on a group call.In all these cases, paging is based on addressing, for example, a groupaddress, a fleet address, an individual address, a set of individualaddresses or addresses within a certain range or address segment. Eithertemporary of permanent addresses can be used.

[0007] Generally, the purpose of the paging is also indicated to theterminal e.g. for a mobile UE terminated phone call, a mobile terminatedShort Message (SMS), an alpha-numeric message to be displayed on apager.

[0008] Positioning or location techniques based on radio signalmeasurements in support of Location based services (LCS) are known forwireless cellular telecommunications systems, for example from thestandard 3G TS 25.305 version 3.1.0 release 1999 “FunctionalSpecification of Location Services”. A general description of locationservices and the service requirements is given in the specification 3GTS 22.071. Generally there are four categories of usage of the locationservice:

[0009] Commercial LCS (or Value Added Services);

[0010] Internal LCS (within the network);

[0011] Emergency LCS;

[0012] Lawful Intercept LCS.

[0013] Two basic techniques are used for determining the location ofmobile user equipment:

[0014] a Mobile based, where the mobile UE can autonomously (e.g. usinga Global Positioning System (GPS) receiver) or with the support of thenetwork (through broadcast of information) calculates its position andtransmits it to the network.

[0015] Network based, where the mobile UE reports measurements of radiosignals and the network can perform the calculation of the mobile UE'sposition.

[0016] By measuring radio signals the capability to determine thegeographic location of the user equipment (UE) can be provided. Locatingthe UE involves two main steps:

[0017] signal measurements; and

[0018] location estimate computation based on the measurements.

[0019] The signal measurements may be made by the UE, a base station ora dedicated location measuring unit (LMU). The basic signals measuredare typically radio transmissions, but some optional methods may makeuse of other transmissions such as general radio navigation signals. Thelocation estimate computation may be made in the UE or by a calculationfunction located in the network. The location information may berequested by and reported to a client (application) associated with theUE, or by a client within or attached to the network. The locationinformation may also be utilised internally within the network, forexample, for location assisted handover or to support other featuressuch as home location billing. There are many different possible usesfor the location information. The location feature may be usedinternally by the network (or attached networks), by value-added networkservices, by the UE itself or through the network, and by “third party”services. The feature may also be used by an emergency service (whichmay be mandated or “value-added”), but the location service is notexclusively for emergencies.

[0020] These systems rely on a calculation of the mobile terminal'sposition which is calculated or recorded in the network. This methodbrings security problems—it is not always the case that a mobile userwants to have the location of the mobile identified by any servicewishing to know it. Further, it takes up network resources to store thelocation of these equipments.

[0021] Positioning or location techniques have also been envisaged as atrigger to handovers, and also as means to support network planning i.e.having the UE report means to determine its position along with radiomeasurements so that the quality of reception can be logged by thenetwork for each position of the mobile.

[0022] One method of determining the location of a UE is known as theCell ID based method. A geographical area for a wireless cellularcommunications system is generally divided into separate radio coverageareas or cells. Generally a base station is located in each cell and amobile user equipment (UE) communicates with one or more base stationtransceivers located in one or more cells during an active call.Generally, from a paging and network organisation point of view, severalcells may be grouped together and referred to as a location area.Generally, the location of a UE within a location area is not knownprecisely. If a UE leaves a location area it will normally registeritself with the new location area via the cell in which it is currentlylocated (Location Updating). Both location areas and base stationsgenerally have an identifier (LAI, Location Area Identifier and BSI,Base Station Identifier) which are generally transmitted on a commonsignalling channel). Except under special circumstances, the networkdoes not know the position of the UE any more accurately than this.Hence, if the network wishes to make contact with the UE it generallysends a paging request on a suitable (usually common) signalling channelstarting with the cells of the last location area in which the relevantUE registered. Location updating causes updating of subscriber data ofthe UE in question in the subscriber database, typically in a VLR,Visitor Location Register associated with a Mobile Exchange (MSC).Hence, it can be stated that the location updating procedure stores alocation of each UE accessing the system. This results in a great dealof data to be stored continuously and the need for signalling at eachlocation update. As the location area is made smaller, the amount ofsignalling increases as UE's move from one location area to the next ata higher frequency. For this reason location areas are typically ratherlarge, usually several cells in size. Such a large size does not allowservices to be provided which depend upon paging UE's in smaller areas,say 200 to 2000 meters in diameter. Known systems in which the positionof a mobile UE is determined by the network based on information fromthe mobile UE have the disadvantage that, if a large geographical areais involved, the positions of a large number of mobile UE's must bestored and continuously updated. This poses impractical limitations onimplementing such a system for anything less than large areas. Anexample of this type of system is described in WO94/07337 in which aTemporary Paging Area reference is stored in the subscriber database.

[0023] The present invention has as an object, the provision of a systemand method for organising a wireless communications system which allowsnotifications of a single user equipment or a group of user equipmentswithin a specified geographical area.

[0024] A further object of the present invention is the provision of asystem and method for organising a wireless communications system whichallows notification of a group of user equipments within a specifiedgeographical area which can be selectable in size without having tostore and update the locations of the mobile UE's within the area.

[0025] A further object of the present invention is the provision of asystem and method for organising a wireless communications system whichallows a user to decide on whether the location of the user equipment ismade known to the network.

SUMMARY OF THE PRESENT INVENTION

[0026] The present invention provides a wireless telecommunicationsnetwork comprising at least one transmitter and a plurality of userequipments able to receive radio messages from the at least onetransmitter, the network being adapted to transmit a notificationmessage to at least a sub-group of the user equipments, a first part ofthe message comprising a representation from which a user equipment candetermine whether its present location is within a certain geographicalarea; and to read a second part of the message in accordance with theresult of the determination.

[0027] The present invention provides a method of operating a wirelesstelecommunications network comprising at least one transmitter and aplurality of user equipments able to receive radio messages from the atleast one transmitter, the method comprising:

[0028] transmitting a notification message to at least a sub-group ofthe user equipments, a first part of the message comprising arepresentation from which a user equipment can determine whether itspresent location is within a certain geographical area;

[0029] at least the sub-group of the user equipments receiving themessage and determining whether the sub-group of user equipments readinga second part of the message in accordance with the result of thedetermination.

[0030] The present invention also includes a mobile user equipment foruse with a wireless telecommunications network comprising at least onetransmitter, the user equipment comprising:

[0031] an antenna for receiving a notification message from the at leastone transmitter, a first part of the message including a representationfrom which the user equipment can determine whether its present locationis within a certain geographical area;

[0032] a means for determining whether the present location of the userequipment is within the geographical area; and a means for reading asecond part of the message in response to the determination.

[0033] The present invention also provides a method of operating amobile user equipment for use with a wireless telecommunications networkcomprising at least one transmitter, the method comprising the steps of:

[0034] receiving a message from the at least one transmitter, a firstpart of the message including a representation from which the userequipment can determine whether its present location is within a certaingeographical area;

[0035] determining whether the location of the user equipment is withinthe geographical area; and

[0036] reading a second part of the message in response to thedetermination.

[0037] The present invention also provides a transmitter for use in awireless telecommunications network for transmitting radio messages toat least one user equipment, the transmitter being adapted to transienta two-part notification message, a first part of the message including arepresentation from which a user equipment can determine whether itspresent position is within a geographical area and a second partcontaining information relevant to the geographical area.

[0038] The present invention also provides a method of operating atransmitter for use in a wireless telecommunications network fortransmitting to at least one user equipment, the method comprising thesteps of: the transmitter transmitting a two-part notification message,a first part of the message including a representation from which theuser equipment can determine whether its present position is within ageographical area and a second part containing information relevant tothe geographical area.

[0039] The transmitter described above may be a base station transmitterused for conventional voice and data transmissions to user equipment. Itmay however, also be an independent transmitter which is specially usedfor transmitting notification messages according to the presentinvention. The representations included in the notification message arepreferably time differences between transmissions from pairs of basestations of the system. Preferably, three time differences are includedin the notification message thus providing a form of triangulation fromwhich a user equipment can decide whether it is a defined geographicallocation without excessive computational effort.

[0040] The dependent claims define independent embodiments of thepresent invention. The present invention will now be described withreference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is a schematic representation of a plurality of basestation transmitters transmitting a paging message including arepresentation of the co-ordinates of a geographical region and theregion defined thereby.

[0042]FIG. 2 is a schematic representation of a part of a user equipmentin accordance with an embodiment of the present invention.

[0043]FIG. 3 is a schematic representation of a network with which thepresent invention may be used.

[0044]FIG. 4 is a message flow for LCS in accordance with an embodimentof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The present invention will be described with reference to certainembodiments and with reference to certain drawings but the presentinvention is not limited thereto but only by the claims. The drawingsare schematic and non-limiting.

[0046] The present invention may be applied to wireless communicationsystems such as Public Mobile Radio (PMR) and Cellular Telephone systemsas well as wireless paging systems and satellite communications systemsand to methods of operation thereof. A pager generally has a pagerreceiver, an alphanumeric and/or audio and/or other visual display aswell as an internal memory and a computing device such as amicroprocessor. A cellular wireless system suitable for use with thepresent invention may be exemplified by the following non-limiting list:AMPS, IS95, GSM (Global System for Mobile Communications), NMT (NordicMobile Telephone), UMTS (Universal Mobile Telecommunication System) andany other system as described for instance in “Wideband CDMA for ThirdGeneration Mobile Communications”, Ojanperä and Prasad, Ailech house,1998. Satellite systems are described for instance in “SatelliteCommunications Systems”, G. Maral and M. Bousquet, Wiley, 1998. In thefollowing, the present invention will mainly be described with referenceto a cellular wireless communications system but the present inventionis not limited thereto but only by the claims.

[0047] In one aspect of the present invention a method and relatedequipment is provided so that the network can notify all UE's or asub-group of UE's based on their position (e.g. to notify all UE'swithin a certain area, this area not necessarily being the same area asa location area and preferably being a smaller area such as an area ofless than 2,000-5,000 meters diameter) without having to store locationdetails of a large number of UE's, e.g. without having to continuouslystore precise location details of all UE's. The UE's may be located inone or more cells. The UE may have complete control over whether itsposition is made known to the network.

[0048] An embodiment of the present invention includes the followingmethod steps:

[0049] 1. The network builds a notification message using any one of avariety of user equipment addresses including, but not limited to, auniversal address which is recoginised by all UE's, a group address, afleet address, a set of individual addresses or addresses within acertain range or address segment. It could also be one address specificto the support of the positioning feature.

[0050] 2. The network sends a notification message using thenotification address. Within the complete notification message, means toidentify a given geographical area are provided or means from which auser equipment can determine whether its present position is within acertain geographical area. Optionally a reason for notification may alsobe included as well as any other type of message, such as analphanumeric message for the subscriber. Generally, every UE has todecode the paging channel and the notification message may be includedin a paging request.

[0051] 3. UE that receives this notification message determines if it isauthorized to decode the message (for example, it belongs to therelevant group, fleet, address segment etc.) and then compares itsposition with the geographical area derivable from the notificationmessage. The UE may receive and process the message independent ofwhether the UE is in idle mode or is actively communicating with thenetwork. If the UE lies within the geographical area specified, the UEtakes one of a variety of actions. For example, it may display a messageon its own alphanumeric display, or execute an appropriate action, forexample send a random access message to the network indicating thereason for access or sound an alarm or activate another piece ofequipment such as boot up a lap-top computer to which the pager receiveris connected. Typically, the user equipment will be required to accessthe network so that the use of the service may be logged and billed. Theinformation necessary contained in the notification message fordetermining the user terminal geographic location may be encrypted orciphered. This allows the service to be provided on a billed basis andalso allows secrecy to be kept.

[0052] Implicit in this method is the ability of the UE to determine itsown position with reasonable accuracy. It may do this via an on-boardGPS receiver or the network may assist in the self-location of the UE.Once, contacted, the network can then obtain from the user terminal anumber of different types of information, such as signal strengthreceived by the user terminal, reports of time differences betweentransmissions from different base stations, reports on snychronisationor other network information.

[0053] One preferred addressing method for notification is to use anaddress where every UE has to decode the associated paging channel. Astructure of the paging channel could also be defined so that all UE's,whatever their paging group, are made aware that such a group paging hasbeen made e.g. one bit on all paging messages could indicate that allterminals have to read a full cycle of paging messages.

[0054] A specific group paging address can also be associated with agiven service e.g. paging addresses address certain service capabilitiesinstead of a UE address. The notification message can be tagged inaccordance with a specific service as well as containing geographicalreference information. As an example, a specific paging reference oraddress can be allocated to a feature such as paging on locationcoordinates in accordance with the present invention. All UE'ssupporting such a feature would then be capable of recognisinig thatreference or address and of decoding the contents of the paging messagefrom which they can obtain the geographic data necessary to determine ifthe message is one relevant to that UE.

[0055] Apart from the paging group address, the paging message containsmeans to identify a geographical location, either a point location or anarea. An example, is a geographical area which includes a shopping mall.Information relevant to that shopping mall may be selectively sent onlyto mobile terminals within the geographical area of the shopping mall.Several means are included within the scope of the present invention, ofwhich the following is a non-limiting list:

[0056] A definition of one geographical area based on geographicalco-ordinates. The UE would support mobile based position locationmethods in which the network provides information for the UE to locateitself autonomously. An example may the latitude and longitude of apoint or a set of latitudes and longitudes which define an area, e.g. aset of three for a triangle, a set of four for a square oblong,parallelogram, or similar polygon. Alternatively, the latitude andlongitude of a point is specified with an additional distance. Thedistance defines the radius of a circle having its centre as thespecified point. Alternatively, a latitude and longitude is given and anoffset from both the latitude and longitude. If the latitude andlongitude of the UE both lie within the region defined by the latitudeand longitude and the offsets thereof, the UE decodes the pagingmessage.

[0057] A list of information on radio signal measurements, where thematching of the radio signal measurements made by the UE with theseradio measurements would be the criterion for the UE to decode thepaging message. The radio signal measurements would identify therelevant geographical area. Examples follow.

[0058] An advantageous means to identify a geographical area is a listof time intervals, e.g. propagation time delays or relative propagationtime delays to identified base stations. The paging message would theninclude a set of time delays and a set of associated base stations (e.g.defined by base station identifiers). Where all the paged UE's are inone cell, one time interval may be representative of the relativepropagation time difference to the base station of the current cell.Other time signals could be representative of propagation delaysassociated with a neighboring cell or cells with which the UE can makeradio signal measurements. As each delay relates to a distance, a numberof such delays from different base stations provides a triangulationsystem which can identify a point if the plurality of distances from thebase stations all coincide at one point, or an area if they do not. Atypical number of signal measurements required to provide adequatetriangulation is 3 to be enough for a given reliability. Where a pointis defined by the information in the paging message, a further distancemay also be transmitted in the paging message, this distance defining aradius around the identified point in order to define a geographicalarea. The UE then compares its position with the identified pint anddetermines if its location lies within the circle defined by the pointand the transmitted distance information as radius of the circle.

[0059] The above techniques involving latitudes, longitudes anddistances can involve complex calculations such as sin, cosine, orsquare root functions. The use of look-up tables to define values ofsuch functions is imprecise. A preferred embodiment of the presentinvention only involves comparisons of values and no calculations oftrigonometric or complex algebraic functions. This may be achieved bythe paging message including a set of time delays or differences asmeasured with respect to a set of base stations. Alternatively, thepaging message may specify a range of time delays or differences whichdefine the required area. This range may be defined by a % of the timedelays or time differences, by an absolute tolerance or range of eachtime delay or difference or by any similar method. By default, apre-defined % or absolute tolerance may be stored in the UE.

[0060] A time delay may determine a distance to a base station. A UE maydetermine the time delay to an identified base station by measuring theround trip time of a message from the UE to the respective base stationand back. However, such a measurement requires the mobile terminal to becommunicating with the system. An alternative is that the UE has asource of accurate time with which it can compare the arrival time ofmessages from a base station and from which it can calculate the timedifferences. Such an accurate clock may be provided by the network forUE's over the air interface or by other radio transmitted clocks.

[0061] More preferred is a reference in the notification message torelative transmission time differences between groups a of base stationspairs, i.e. the difference in time taken for a signal to travel from afirst base station and a second base station to the UE. In either case,the time delay defines the locus of a point along which the specifiedtime difference is true. By specifying two or more delays or timedifferences two or more loci arc defined. Their point of intersectionthen defines the relevant geographical point. Preferably, theintersection of three such loci is used to define the geographical area.FIG. 1 is a schematic representation of a group of cells of a wirelesstelecommunications system with a base station transceiver at the centreof each cell. A notification signal is built in the Mobile Exchange MSCand broadcast from the three transmitters T₁, T₂, T₃. The messagedefines (in a first part of the message) three or more negativetolerances δTD₁₂, δTD₂₃, δTD₃₁ and three or more time differences TD₁₂,TD₂₃, TD₃₁, which are the time differences between transmissions frompairs of base stations 1 and 2, 2 and 3 and 3 and 1, respectively. Thesetime differences arc defined in certain standards, e.g. they arereferred to as “Observed Time Differences” OTD in standard TS 25.305.These representations define regions R₁, R₂, R₃ with respect to therelevant transmitting base station pairs T₁₂, T₂₃, T₃₁. Where the threeregions R1, R2, R3 overlap, a region A is defined. Hence, by giving thetime differences TD₁₂, TD₂₃, TD₃₁ and a tolerance on each of these,δTD₁₂, δTD₂₃, δTD₃, the notification message includes representationsfrom which the UE 1 can deduce whether or not it is in the region A.

[0062] The loci actually define a figure in three dimensions, ahyperboloid. For location service in three dimensions the hyperboloidmust be considered. The geometry of the base station locations mayaffect the accuracy of the location estimate. The best results are whenthe base stations equally surround the UE. If they do not, there is areduction in accuracy, which is sometimes termed the Geometric Dilutionof Position (GDP).

[0063] Each UE 1 authorised to decode a first part of the paging messageextracts the time difference information TD₁₂, TD₂₃, TD₃₁; δTD₁₂, δTD₂₃,δTD₃₁ and references to the base stations T₁, T₂, T₃ and compares actualtime difference measurements for these base stations at the UE 1 withthe transmitted values. If each measured time difference MTD₁₂, MTD₂₃,MTD₃₁ lies within the respective range TD₁₂ to TD₁₂-δTD₁₂, TD₂₃ toTD₂₃-δTD₂₃, TD₃₁ to TD₃₁-δTD₃₁, the UE 1 assumes it is within thespecified geographical region A and decodes the rest of the notificationmessage. Instead of providing a time difference TD and an offset δTD,two different time differences TD¹ and TD² could be transmitted wherebythe difference between the two is the offset. In addition, a referencenumber, code or identification may be included in the notificationmessage. This can be used to distinguish different notification messageswith representations of co-ordinates relating to differing geographicalareas in one cell. The UE's can reply to the network giving thereference code so that the network can identify which mobile UE's areanswering to which notification message.

[0064] In order to calculate the representations which are to beincluded in the notification message, it is necessary to know:

[0065] the surveyed geographic locations of the base stations that havehad their signals measured; and

[0066] the actual relative time difference (RTD) between thetransmissions of the base stations (caused by offset, asynchronicity) atthe time the notification message will be sent.

[0067] The accuracy of each of these measurements contributes to theoverall accuracy of the location estimate. There are several approachesto determining the RTD. One is to snychronise the transmissions of thebase stations. In this technique the RTD are known constant values thatmay be entered in a database and used when making a location estimate.The snychronisation must be done to a level of accuracy of the order oftens of nanoseconds (as 10 nanoseconds uncertainty contributes 3 metreserror in the location estimate). Drift and jitter in the synchronizationtiming must also be well controlled as these also contribute uncertaintyin the location estimate. Snychronisation to this level of accuracy iscurrently available through satellite based time-transfer techniques.The transmission times may all be aligned to a common reference in whichcase all RTD have a common value. However, in a more general case thetransmissions may have a fixed offset with reference to the referenceand thus the RTD values are non-zero and may be stored in the database.

[0068] It is preferable that the location methods do not require thebase station network to be synchronized. The base stations may be leftto free run within some constraint of maximum frequency error. In thiscase, the RTD will change (slowly) with time. The rate of change willdepend on the frequency difference and jitter between base stations. If,for example, the maximum frequency difference between two base stationsis ±10 ⁻⁹, then the start of transmission of a 10 millisecond codesequence will drift through a cycle in about 1 390 hours (or 57 days).With this relatively slow rate of drift the RTD can be measured usingfixed measuring units at known locations and stored in the database. Thejitter and drift of the individual oscillators in each base station maycause the change of timing to slow, remain constant or reverse directionover time. Ongoing measurements of the RTD may be made to assure themost current values are available for the calculation function. The RTDmeasurement units may be co-located with the base stations or installedat other convenient locations in the coverage area, and report theirresults through network signalling channels.

[0069] If there are frequency differences between unsynchronised basestations, the RTD used in the calculations for the representations to beincluded in the notification message should be determined only a shorttime before the notification message is sent. In order to assure lessthan a 20 nanosecond uncertainty in the RTD value, the message must besent within 10 seconds if the maximum frequency difference between thebase stations is ±10⁻⁹.

[0070] If the geographical area derivable from the notification messageis large, the notification message in accordance with the presentinvention may trigger a large number of network accesses within a shorttime of transmitting the notification message. Such a large number maydisturb the operation of the relevant cell or even block its operationfor other users. In accordance with a further embodiment of the presentinvention, each mobile UE is adapted to delay reply to the notificationmessage by a random time delay. By suitably dimensioning this delay, theaccess rush can be spread over a reasonable length of time, thisavoiding blocking of the cell operation.

[0071] UE's supporting LCS in Idle mode may run the necessary set ofradio signal measurements permanently so as to trigger applications onthe internal memory of the UE (e.g. SIM memory) in need of such locationinformation (mobile based positioning). For such UE's, thesemeasurements would suffice.

[0072] Regarding other terminals, the need to perform prior andbackground radio signal measurements in support of the method inaccordance with the present invention could be carried out permanentlyor only when indicated on a suitable common signalling channeltransmitted from one or more base stations. Such a common signallingchannel can be the beacon channel (BCCH) or pilot signal transmittedfrom each base station. Alternatively, such measurements need notnecessarily be prepared in advance and be performed only on receipt ofthe notification message containing the distance or time information.

[0073] With respect to a network using Code Division Multiple Access(CDMA) on the air interface, a UE near its serving base station cannothear other base stations on the same frequency. In order to determineaccurately if the UE location is within the specified region, the UEterminal should be able to receive at least three base stations. Tofacilitate this sonic special means may be required. A solution for theabove mentioned hearability problem is the IPDL (Idle Period DownLink)method. In this method each base station ceases its transmission forshort periods of time (idle periods). During an idle period of a basestation, terminals within the cell can measure other base stations andthe hearability problem is reduced. Also, during idle periods real timedifference measurements on the base stations can be carried out todetermine any offsets or asynchronicity. Because the IPDL method isbased on forward link (downlink) the location service can be providedefficiently to a large number of terminals simultaneously.

[0074] The Idle Periods may be arranged in a predetermined pseudo randomfashion according to higher layer parameters. These parameters are usedby the transport layer to arrange and use these Idle Periods. IdlePeriods continuous mode or burst mode. In continuous mode the IdlePeriods are active all the time. In burst mode the Idle Periods arearranged in bursts where each burst contains enough Idle Periods toallow a UE to make sufficient measurements for it to determine if it isin the specified location. The bursts are separated by a period where noIdle Periods occur.

[0075] The notification message in accordance with the present inventionmay be included in any suitable message. Thus, it may be included withinnormal paging messages. However, it may also be included within othermessages. Cellular telephone systems often have a capability to addressall UE's in a cell by means of a Cell Broadcast message. Such a servicemay also be used to broadcast the co-ordinates of the geographical areaof interest in accordance with an embodiment of the present invention.UE's which identify that they are within the geographical area then takethe appropriate action, e.g. activate an alarm, display a message ormake contact with the base station of the cell. Generally, the UE willbe required to contact the network so that the use of the service can belogged and billed. To allow user decision, the arrival of thenotification message may be displayed on an alphanumeric display with arequest if the user wishes to accept it (and hence incur charges). Inorder to avoid user disturbance when the notification message is sentrepeatedly, the UE may be configured to ignore all notification messageswith a specific reference number after the message has been rejected oraccepted once. This ignoring of a notification message may be linked toa timer so that after a while the UE allows receipt of the messageagain.

[0076]FIG. 2 shows a general block diagram of a receiver 10 of a userequipment (UE) 1 in accordance with an embodiment of the presentinvention. The UE 1 comprises a receiver 2 connected to an antenna 3.Operation of the UE 1 is controlled by a processing engine 5 such as amicroprocessor. The receiver 2 may be connected to analog to digitalcircuits 6 for pre-processing a received analog radio signal fromantenna 2 and outputting a digital signal to the processing engine 5. Auser interface may optionally include a display 7 and optionally akeyboard 8 and may optionally be connected to loud speaker 4. Messagesreceived by antenna 3 are delivered to the processing engine 5 via theanalog to digital circuits 6 and receiver 2. Software programs may berun on processing engine 5 to carry out the methods of the inventiondescribed above.

[0077] Ancillary equipment 9 may be coupled to the processing engine 5and/or the antenna 2. The ancillary equipment may be a transmitter andtransmission circuitry of a mobile telephone to provide both receive andtransmit functions under the control of the processing engine 5.

[0078]FIG. 3 is a schematic representation of a network with which thepresent invention may be used showing the general arrangement of theLocation Service feature. This illustrates, generally, the relation orLCS Clients and servers in a network. The LCS entities such as servers12, 14 and an LCS client 18 communicate with across various interfacessuch as with a PLMN 20 with Mobile Switching Centres (MSC) 22 or ServingGPRS Support Node (SGSN) 24 and then over the Iu interface with othernetwork elements such as Radio Node Controllers (RNC) 26, and the fixedtransceiver sites (Node B) 28. As part of their service or operation,the LCS Clients may request whether User Equipments (UE) or mobilestations are within a certain geographical location. There may be morethan one LCS client and these may be associated with the network,operated as part of a UE application or accessed by the UE through itsaccess to an application (e.g. through the Internet). Typically theserving RNC, receives authenticated requests for LCS information from anetwork across the Iu interface. LCS entities then manage the networkresources, including the Node-B's 28 (base stations), and the UE, toreceive a list of UE's within the specified geographical area.

[0079] Upon request from the LCS entities or for internal networkoperations, the network will:

[0080] determine or calculate the representations which are to be sentin a notification message which will allow a User Equipment to decide ifthe UE is within the geographical area requested by the LCS or networkinternal entity;

[0081] transmit the notification message;

[0082] send the results as a list of the UE's which respond to thenotification message to the LCS entities or to application entitieswithin network.

[0083] A message flow is shown schematically in FIG. 4. The operationbegins (1) with an authenticated request for location information aboutUE's from an application in the network being received at the networkLocation System Control Function (LSCF) in the serving RNC (SRNC). TheLSCF acts as interface between the network and the LCS entities.

[0084] 2. The LSCF considers the request and the capabilities of the UEand the network and forwards the request to the appropriate PositionRadio Calculation Function (PRCF) in the Serving RNC.

[0085] 3. The PRCF builds the representations required for thenotification message and sends this to the UE's via the relevant Node-B.

[0086] 4. The UE's receive the message and determine in a MobileCalculating Function (MCF) whether they are in the requested region. Therelevant UE's which wish to accept the notification return an acceptanceto the PRCF.

[0087] 5. The PRCF may request additional data about the associatedtransmitters to be used in the notification message from a LocationSystems Operation Function (LSOF) database. Data necessary for theaccurate calculation of the time differences to be used in thenotification message (Real Time Differences, RTD) may depend on timingoffsets and synchronicity between base stations and this data is storedin the LSOF database. This data may be stored locally to the RNC if theyare constant over time, otherwise they can be updated to represent theRTD timing at the time-of-day the notification message will be sent.

[0088] 6. The LSOF returns the timing data requested.

[0089] 7. The PRCF sends the list of UE's to the LSCF.

[0090] 8. The LSCF passes the list to the LCS client via the network.

[0091] The above scheme has considerable advantages in comparison withknown techniques. It is not necessary to contact UE's individually. Acell broadcast or similar broadcast message may be sent to all UE's in acell. Only the relevant UE's respond and a response also automaticallyincludes an acceptance of the service which allows privacy of the user(by not accepting).

[0092] The skilled person will appreciate that there are variousmodifications to the above scheme all of which lie within the scope ofthe present invention. For use in the calculation of the representationsin the notification messages, the relevant calculating function (PRCF)within the RNC may require additional information. This may be obtainedby the function directly by communication with a database, as indicatedabove, or it may be through a request to LCS entities that will mediatethe request and return of information from the appropriate database (ordatabases if more than one is needed to fulfil the requests). There maypossibly also be available independent information that is able tosupply the location information directly, or may be able to supplyauxiliary information to the calculation function.

[0093] The utility of methods and apparatus in accordance with thepresent invention can be demonstrated in a variety of ways:

[0094] Network planning: the network can decide to optimise the networkplanning for a given area, and therefore requests terminals within thatarea to contact it so that the network can receive signal measurementsfrom the terminal, along with the terminal information on its position.

[0095] Emergency calls: the network, on receipt of an emergency callfrom a mobile or stationary UE, can page all mobile UE's within the areawhere the calling user is, and collect from this the list of terminalidentities (based on temporary identities such as TMSI or permanentidentities such as IMSI) within that area. This could be useful in caseof further investigation by the police so that witnesses may be sent tothe scene of the emergency.

[0096] Fleet management, where there is a need to find the closest UE toa specific location e.g. to send a taxi, an ambulance, or a police carto a given location.

[0097] Precise warnings: where there is an emergency situation, e.g. anuclear or chemical accident, UE's within a danger zone may be alerted.The users of these devices could alert others in the area not havingmobile telephones or pagers.

[0098] Activation of devices: armaments (canons, mines, mortars),fireworks, alarms or other equipment could be activated remotely withouthaving to address each device separately.

[0099] It is also possible to use the methods in accordance with thepresent invention to perform “permanent” paging, i.e. send in a CellBroadcast message of a cell the coordinates ordinates of one area withinthe cell. On detection by the terminal that it has entered such an area,the terminal accesses the base station of cell to receive instructions.

[0100] It will be clear from the above that the network does not need tostore data concerning the precise location of mobile users other thanthe information already stored for location of the user for conventionalpaging. Hence, services enabled by the present invention are providedwithout major changes to the amount of data stored by the network andwithout influencing the frequency of location updates.

[0101] The user can decide at all times whether or not the location ofhis or her user equipment is made known to the network. This guaranteesprivacy, a problem with existing LCS systems.

[0102] While the present invention has been shown and described withreference to preferred embodiments, it will be understood by thoseskilled in the art that various changes or modifications in form anddetail may be made without departing from the scope and spirit of thisinvention. For instance, in the methods described above the UEdetermines if it is within a certain specified area and takes action ifit is. The UE may be adapted to take action in the inverse case, that isif it is not within the specified area and to take no action if it iswithin the specified area.

[0103] Also in the above reference has been made to base stationtransceivers of a cellular system transmitting the notification message.The present invention is not limited thereto. For instance, thenotification message could be sent by special transmitters which arereserved for this purpose. These may be distributed more or less oftenthan existing base stations or may be added as additional equipment ateach base station.

[0104] In the above mention has been made of a UE measuring timedifferences between transmissions from base stations. InsteadPositioning Elements (PE) may be located within the coverage area. PE'sare placed in accurately known locations other than those of the Node Bequipment. They synchronise to the downlink in a cell and transmit theirsymbols at predefined—or signalled—offsets with regard to the arrival ofthe beginning of a transmission from the base station of the cell, e.g.the beginning of the beacon or pilot frame at the PE location. Each PEmay transmit a different and identifying code. The time difference whichis observed and used by the UE to decide whether it is in the requestedarea is the difference—with respect to the time of arrival at theUE—between the a transmission from the base station of the serving celland the transmission from a PE. The measurements can be used to estimatethe UE distance to the Pc's.

1. A wireless telecommunications network comprising at least one basestation transmitter and a plurality of user equipments able to receiveradio messages from the at least one base station transmitter, thenetwork being adapted to transmit a notification message to at least asub-group of the user equipments, a first part of the message comprisinga representation from which a user equipment can determine whether itspresent location is within a certain geographical area, and to read asecond part of the message in accordance with the result of thedetermination.
 2. The wireless network according to claim 1, wherein atleast the sub-group of the user equipments is adapted to receive thenotification message and to determine whether their present location iswithin the geographical area.
 3. The wireless network according to claim1 or 2, wherein the network is a cellular wireless network and thegeographical area is smaller than a cell of the network.
 4. The wirelessnetwork according to any of the previous claims, wherein therepresentation comprises a definition of the geographical area.
 5. Thewireless network according to any of claims 1 to 3, wherein therepresentation comprises a set of time data and references to radiotransmitters of a set of radio transmitters.
 6. The wireless networkaccording to claim 5, wherein the time data are time differencesrelating to pairs of radio transmitters.
 7. A method of operating awireless telecommunications network comprising at least one base stationtransmitter and a plurality of user equipments able to receive radiomessages from the at least one base station transmitter, the methodcomprising: transmitting a notification message to at least a sub-groupof the user equipments, a first part of the message comprising arepresentation from which a user equipment can determine whether itspresent location is within a certain geographical area; at least thesub-group of the user equipment, receiving the message and determiningwhether their present location is within the geographical area; and thesub-group of user equipments reading a second part of the message inaccordance with the result of the determination.
 8. The method accordingto claim 7, wherein the network is a cellular wireless network and thegeographical area is smaller than a cell of the network.
 9. The methodaccording to any of the claims 7 and 8, wherein the representationcomprises a definition of the geographical area.
 10. The methodaccording to any of the claims 7 to 9, wherein the representationcomprises a set of time data and references to radio transmitters of aset of radio transmitters.
 11. The method according to any of the claims7 to 10, wherein the time data are time differences relating to pairs ofradio transmitters.
 12. The method according to claim 11, wherein a userequipment carries out time difference measurements on the transmissionsfrom the pairs of radio transmitters and compares the measureddifferences with the representations in the notification message.
 13. Amobile user equipment for use with a wireless telecommunications networkcomprising at least one base station transmitter, the user equipmentcomprising: an antenna for receiving a notification message from thebase station transmitter, a first part of the message including arepresentation from which the user equipment can determine whether itspresent location is within a certain geographical area; a means fordetermining whether the present location of the user equipment is withinthe geographical are; and a means for reading a second part of themessage in response to the determination.
 14. A method of operating amobile user equipment for use with a wireless telecommunications networkcomprising at least one base station transmitters the method comprisingthe steps of: receiving a message from the base station transmitter, afirst part of the message including a representation from which the userequipment can determine whether its present location is within a certaingeographical area; determining whether the location of the userequipment is within the geographical area; and reading a second part ofthe message in response to the determination.
 15. A base stationtransmitter for use in a wireless telecommunications network fortransmitting messages to at least one user equipment, the transmitterbeing adapted to transmit a two-part notification message, a first partof the message including a representation from which a user equipmentcan determine whether its present position is within a geographical areaand a second part containing information relevant to the geographicalarea.
 16. A method of operating a base station transmitter for use in awireless telecommunications network for transmitting to at least oneuser equipment, the method comprising the steps of: the transmittertransmitting a two-part notification message, a first part of themessage including a representation from which the user equipment candetermine whether its present position is within a geographical area anda second part containing information relevant to the geographical area.